Gearing



Dec, 4,193.4:1

Y R. STEvENsoN 1,982,768

c-EABING.

Filed Sept. 15, 1950` 5 Sheets-Sheet 1 Dec- 4, 1934- r R. sTEvENsoN GEARING Filed Sep'.. l5, 1950' 3 Sheets-Sheet 2 R. STEVENSON Dec. 4, 1934.` l

,GEARING 5 sheets-sheet s Patented Dec. 4, 1934 PATENT OFFICE,

GEA

RING

Robert Stevenson, West Barrington, R. I., assignor to M & S Manufacturing Co. Inc., Providence, R. I., a corporation of Rhode Island Application September`15, 1930, Serial No. 481,953

4 Claims.

My invention relates'to improvements in gearing, `particularly of the type Where one' member is used to rotate another at substantially right anglesr thereto, and Where it is desired that the second member be not able to rotate the first member. While my invention may be used for various purposes, it is particularly adapted for use in steering mechanisms, particularly those of the type adapted foruse in.automobiles,motorboats, aeroplanes, etc.

l I preferably employ a worm on the steering shaft or other shaft employed, and a Worm gear on the crank shaft or other shaft employed for moving` the steering rods or other mechanism and one feature of my invention relates to the specic construction of Worm and Worm gear` employed .for this purpose, anda circular Worm are employed, itis obvious thatudue to their inherent construction, only a very small portion of the periphery of the worm gearcan be in mesh With the Worm at the same time. In vorder that a greater number of Worm Igear-teeth .may enmesh with the teeth on the worm, I provide preferably a hemitorical concavity Vin the side `Wall of the Worm and provide acontinuous spiral groovelin said concavity preferably of constant pitch along the surface of said concavity and preferably inclined so as to be Vradial relative to the center line of said concavity, and I preferably `employ a ycooperating -worme-gear of a radius substantially equal to that of the .concavity,having a plurality of spaced .preferably stud `teeth of a pitch substantially equal to that of the groove on the periphery of the Wormzriding in said groove. j

In'the specification and claims I employ the Word torical to signify of torus shape. With thisy construction it is obvious that a larger portion of the periphery `ofthe 4Worm gear, byy means of its plurality of teeth will be in mesh With the ,groovein the `torical concavity on the Worm.

Even supposing, that in a cylindrical worm, a plurality of VWorm gear teeth. are in mesh therewith, Yinasmuch as the periphery of the worm gear is circular, Whereas the intermeshing side ofthe worm is cylindrical, it is obvious that one tooth only'Will sinkits full depth into the Worm groove, whereas theV other teeth Will only be partiallyin the groove. With my construction, however, it is obvious that all of the contacting teeth in the Worm gear Will be ycompletely in meshwith the A Iteethof'the worm at all times.

Where a circular worm gear` vided a much stronger lstructure than any provided hitherto, because in my preferred embodiment the teeth on substantially half of the periphery of the Worm'gear are in mesh with vthe groove in the worm. In general, my invention is an improvement on the so-called Hindley type of gearing. Whereas the Hindley type of gearing `had a concavity in the Worm, the teeth on the Worm gear were constructed With'a plurality of straight 'circular rib threads extending around the'periphery thereof thus providing plane contacts with the sides of the-groove. In practice it has been 4found that these circular teeth have not Worked efficiently with a Worm of this description. In addition, inthe Hindley gear, the pitch has not 4been takenalong-the arcuate line of the concavity, 'which has prevented'the groove from being inclined so as to be radial relative to the `center line of said concavity. l

I believe that I am the first, therefore, to provide a Wormof this description in which the grooves are cut in underneath their outerperipheral `portion vin my preferred embodiment so as to be radial relative to the center line of the concavity. This provides, Vinmy improved type of Worm an irreversible feature which willy be-described in more detaillater. v lA further feature of `my invention relates t the fact that I employ-in my worml gear which as stated is preferably of a radius substantially equal to that of the concavity, preferably a pluralityof spaced stud teeth having curved or otherwise broken side Walls so as to provide line .contacts with the sides of thegroove of apitch substantially equal to that of the groove on at least, preferably half of the periphery thereof to ride in said groove. Whereas, an ordinary rib tooth with fiat sides as normally employed on a Worm. gear-has difficulty in getting out of mesh with a straight Hindleytype of worm, by employing, preferably frustro-conical stud teeth or other teeth having line contacts'only with the side walls of the groove, it is-obvious thatthey may readily ride out of the groove. By employing this, construction, of'having a grooved Worm with thegroove of thevworm inclined so-as to be radial relative'to the center line of the concavity and With Athe line contact stud'teeth ontheworm gear, I am enabled to achieve a new result, When o-ne of thestuds reaches a portion of the groove so inclined that the turning component ofthe forceexerted bythe Wormgear will not overcome the worm frictionV tofturn the worm, it is obvious that :movements of the Worm gear that connects thefcrank shaftwillnot cause v`^move- Too ment of the worm and steering rod, thus providing in a steering mechanism a very desirable feature and preventing the wheel from turning, when an extraordinary force is exerted on the crank shaft, such as by the bursting of a tire.

I am aware that others have attempted to do this by constructing the cooperating ordinary worm and worm gear on the steering rod and crank shaft of very low pitch. With my construction, however, it is possible to provide a fast pitch on the steering rod worm and the crank shaft worm gear thus making the relative movement of the two shafts quicker or the braking torque exerted by the crank shaft greater on a smaller turning of the steering wheel.

In addition, I preferably employ a plurality of stud teeth, preferably extending more than half way around the periphery of the worm gear and the degree of angularity of the groove changes from right angles when in the center of the concavity, to parallelwith the axis of the steering rod at the extremities of the concavity so that near the ends of the groove any leverage applied to the crank shaft has no effect in turning the worm on the steering rod even when a single tooth is employed and that reaches the extremity of the groove. This is particularly true where a plurality of stud teeth are employed as in my preferred embodiment. In an ordinary worm and worm gear, the pitch line of the worm is straight, that of the worm gear circular. In my improved device, the pitch of both the worm concavity and the worm gear are coincident and circular and I preferably employ the center line of the hemi-torical concavity substantially coincident with the extended theoretical side wall of the worm before the concavity is cut. Itis obvious that the center line of the torical cavity may be moved out and hence any size or partially torioal concavity may be produced, although I have found best results are attained when a substantially hemi-torical concavity is employed.

A further feature of my invention relates to the fact that I preferably split my improved worm into two relatively adjustablev portions, along the axis of said concavity and I provide means to make one of these split worm portions adjustable relative to the worm gear and to move towards the other section to take 'up play and backlash between the worm gear and yworm portions.

Instead of employing a substantially hemitorical concavity, grooved in the manner heretofore explained, in the sidewall of the worm, it is obvious that I may employ a substantially quarter-torical concavity in an end corner of a cylindrical worm; thus providing, in thefinished article, the equivalent of a half portion of centrally split hemi-torical concaved worm and it is apparent that while my invention will not function so perfectly with only substantially a half of my preferred worm, it is obvious that such construction will have many of the advantages thereof.

Further features of my invention relate to the specific means I employ for housing the worm on the lower end of the steering rod and the adjacent portion of the crank shaft and providing means in said housing for adjustment for play and backlash of the worm or worm sections.

A further object of my invention is to distribute the wear of the steering mechanism more evenly over a relatively larger number 'of teeth than formerly thereby lessening the wear and consequent backlash caused thereby.

'vious embodiment.

A further object of my invention is to assist in taking the shimmy out of the steering wheel and to lessen the road shocks before they are transmitted to the steering wheel. These and such other objects of my invention as may hereinafter appear will be best understood from a description of the accompanying drawings which illustrate various embodiments thereof.

In the drawings, Fig. 1 is a perspective view of the exterior of a housing for the lower end of the steering wheel and connecting portions of the .crank shaft employing my invention. Fig. 2 is In the drawings, wherein like characters of reference indicate like parts throughout, 10 generally indicates a worm constructed in accordance with my invention. As stated hitherto, while my improved type of worm is particularly adapted for use in cooperation with my improved type of worm gear, for transmitting rotary movement between two shafts at right angles to each other, it has certain inherent features of construction novel to worms and may be employed in any place where it is possible to use a worm of this description. My improved worm 10 comprises a cylinder having a partially torical concavity 12, preferably a hemi-torical con-cavity in the side wall thereof. It is obvious that if it is a true hemitorioal con-cavity, the center line thereof, will be approximately in the center of the cylinder wall in which the concavity is cut. If, however, the center line thereof is exterior of the cylinder, it is obvious that it will not be a true hemi-torical con-cavity but merely a partially torical con-'cavity.

In my preferred embodiment, said concavity 12 is provided with a cam groove 14 winding as a modified helix. Most worm gears are provided with a true helical cam groove of a linear pitch along the side of the cylinder. In my improved embodiment, however, I employ a cam groove 14 of the con-cavity 12 of constant circular pitch along the arcuate line of said con-cavity.

A further feature of my invention relates to the fact that I preferably incline the side Walls 16 of said groove so that they will be radial relative to the centerline of the con-cavity. I also preferably split my improved worm in to two portions, 1K0a and 10b adjustable relative to each other and preferably split Valong the plane of the centerline of the con-cavity. As shown in Fig.

fis

g1-cove. 'therefore,'I believe that I amthe rst tov provide insomma famed' with fthe f downwardly -projeetewextension lltforfafpurpose later toi be described. n l-Wliiere `'my `improved*worini 11-0` may 'be-em- I played l in yanydesired manner, it is particularly "a lplurality of spaced preferably 4'frustro-conical stud teeth 20 of a circular or arcuate pitcheubstantially equal to that of the groove' in theworm and preferz'iblyiprovided` on at least half of the periphery thereof and adaptedl to ride in said .groove in the worm. `Itis obvious that inasmuch 'as 'the side-walls '16 ofthe groove are `inclined Vso as to berad-ial relative'to the 'center'linefof theconcavity, `that they "will `project outwards andovertheirbase `at the outer portion yof the As distinguishedy from the Hin-'dley gear a worm having such an inclined groove-so asto interlock-with the stud teeth on the wormy gear.

`It is thus apparent thatfthe center portion of'- the groove 14' `will be at approximately rightanglesi to the stecringrod or the othershaft 22 on-which the` worm is mounted butthat as theA groove extends Voutwards onthe con-cavity,'near the end thereof, it will be substantially parallel to the-axis the-worm gear, will not overcome thewormfrlction to cause the worm gear to tu-rn the worm.

IAs a Astu'dtooth approachesthe outer portion ofthe Worm-groove, itfis obviouslthat the chief 'component'of the'force'exerted thereby-*will be utowardsltlie axis ofthe shaft 22 andnotlengthwisethereof 'to cause a turning'movernent, and

thelengthwise 4componentwill become so small that it will be impossible for lmovementot the worm gear 18 to turn the worm 1'2.

Where a plurality of studs are employed on 'the `worm gear, asthere will-always be a vsubstantial number in the groove in each side ofthe concavity, it is'obvi-ous that this locking action will be increased and will be substantially positive at any relative position of the worm and worm gear, particularly if the stud teeth extend around more than half the periphery of the worm gear. While the sides of the groove 14 and the studs 20 may be perpendicular, I preferably construct both the groove 14 with inclined outwardly daring side walls and the studs 20 so that they may be frustro-conical or with curved side walls to provide a line contact with the sides of the groove to insure a closer binding action of the studs Within the groove than hitherto. While my improved worm and worm gear may be used for connecting any transmittal of movement between two shafts preferably at right angles to each other. it is particularly designed and adapted for use for transmitting movement in a steering mechanism between the steering rod 22 thereof and the crank arm or shaft 24 thereof, and I have shown in the drawings an embodiment of my invention particularly adapted for this purpose;

To this end, I provide the substantially cylindrical housing 2S for the lower end of the steering rod 22 and I provide said housing with the upper end internally threaded as at 28. The crank shaft 24 projects through said housing at right angles and adjacent to said steering rod. The crank shaft 24 is provided with the usual torque rarm-125 i'toilwhich. the steering mechanismtrods may beaattached-.a's usual. l

vMy improvedtwormsgear `1.0f isifmountedwithin threhou'singy26 so .asto have the lower-section 10b thereof inthelower -endof the housing and il the upper section 10a immediately ab'oveiit and Vmy improved. Worm/gear' is mounted onl the crank shaft 1124 so that thestu'ds S20 thereof'intermesh Withttheagroove 1'4ron'the worm. The lowerend `lofIthesteering rodztfi22 within the housing 26 is grooved as `at 30 substantially the lengthfofthe lmusing: andthe interior'toff each' of the worm sections la and lbzis' provided 'with a central `,key L:313 lprojecting. inwardly :therefrom .adapted to l0 :and 10b tosbefnonerotatably: mounted on said y:steering rod.:22 :yet `:axially movablyithereon.

'The lowerendtzofthe housing is pro-vided with :'a hearing,`. preferably a roller bearing. 3`6.onrwhi'ch "the lowerxsplit-worm portionv b may ride. This relier" bearing. mayproject obliquely lupwards into tlre'interior .ofthefsplit gear portion` 10b' orv ob- .1 lique'ly :downwards into" the i housing, r in .the emhodi'ment shown, .projecting :obliquely v upwards `from :the lower: end of the housing' intol the split worm portion 10b.

. I provide a cylindrical adjusting block .38 :externallyitlrreaded as fat kl0 adapted1 to' `be threadedlyvcontainedzin thennpper yend ofy said housing and .provided 'with an: adjusting plugpreferably foi heiragorialshape 39 .for aY Wrench `to litI on lthe upper'end lthereof projecting .upwardly ltherefrornfan'dza split, ring :41l projecting integrally upuwardlyifromxsaid plug :39. .The steering rod is fpi'ovid'ed-withuthe usual 'stationary tube i42-lprojectingdcwnwardly from the -wheel and rigidlyfattached' to a vporti-onl ofthe automobile frame.

.The upper `split kwormlsection 10b is` slidfably `splinedf. to the steering rod-@22 by thekeys 33 thereof: riding in; the groove. 30-in theisteeringrod. -A

cooperating set of oblique preferablyv roller bearings 34 are provided between the upper end of ttheasplit ,wormssection l0*L and thelower vvend of itherarljusting block 38-, and-inthewembodiiment :shown these rextend voblftauewardly rdownwardly iinto upper split .worm-portionllol Theup'- per end of the housing 26 is split as at 44 and is provided with means such as a locking bolt 46 for adjustably securing the split portions together around said adjusting block.

It is thus obvious that on turning the preferably hexagonal plug 39 on the upper end of the block 38 by a Wrench or other suitable tool that said block may be screwed downwardly of the upper portion of said housing toforce the upper split worm portion 10a downwards against the worm gear 18 and the lower split worm portion 10b to adjust said split Worm portions, worm gear and bearings for play and backlash. In practice the split sections 10a and 10b are spaced apart suiiiciently so as to form a continuous groove between them perpendicular to the steering rod and a continuation of the groove 14 in which one or all of the teeth may ride. The sections are thus so split and adjusted as to form a continuous groove of even pitch throughout.

When the adjusting block 38 has been screwed down a sufficient amount to adjust the sections l()a and 10b for play and backlash and bearings for play and backlash, it is obvious that the adjusting block 38 may be locked in adjusted position by tightening the adjusting bolt 46 to= bring the upper portion of the housing each side of said split 44 together to tightly lock the block 38 in position and that the split ring 41 projecting upwardly from said block may be tightened around the lower end of the stationary tube 42 by the tightening of the adjusting bolt 43 and joining the split sections thereof together, to secure the upper end of the block to the lower end of said stationary tube.

If desired, the type of worm shown in Figs. 1 to 4 employing a hemi or partially-torical concavity and suitable groove cut therein may not be split but the groove may be formed continuously therein.

While I preferably employ a hemi-torical concavity in the side Wall of the worm, I may as fshown in Fig. 5 employ as-the worm one only .of

the split worm portions shown in Fig. 2, in which case I provide the lower end thereof with an eX- tension 11 suitable to ride on the ball bearings 36 in the lower end of the housing 26 and such a gear is suitable for many purposes, although it is not quite so definite in its locking action as that in the embodiments shown in Figs. 1 to 4. Where only one stud tooth 20 is employed, in adjusting the upper section 10a for play and backlash, it is obvious that the crank shaft 18 will have to be so turned that the stud 20 will lie between the two sections 10a and 10b.

It is thus apparent that I have provided a novel type of worm with the advantages portrayed above and particularly adapted for use in combination with the novel type of worm gear and particularly adapted for use as shown as a torque transmitting connection between one shaft, preferably a steering rod and a shaft to apply torque for steering or other mechanism, and the novel type of means for adjusting such a mechanism for play and backlash as heretofore described.

It is understood that my invention is not limited to the specific embodiments shown and that various deviations may be made therefrom with- 'out departing from the spirit and scope of the appended claims. f

WhatI claim is:-

1. In combination a worm having a partially torical concavity in the side wall thereof having a cam groove in said concavity along the arcuate `line of said concavity with the outer side wall thereof undercut toward the outer edge of said groove relative to planes perpendicular to the axis of the worm, said cam groove extending on both sides of the plane through the minimum diameter of the worm, and a cooperating worm gear of a;

rform line contacts with the side walls of the groove.

2. In combination, a worm having a partially torical concavity in the side wall thereof and having a cam groove in said concavity along the arcuate line of said concavity with the outer side wall thereof undercut toward the outer edge of said groove relative to planes perpendicular to the axis of the worm, said cam groove extending on both sides of the plane through the minimum diameter of the worm, and a cooperating worm gear of a radius substantially equal tothat of the concavity having a plurality of spaced teeth of a pitch substantially equal to that of the groove riding in said groove and having curved side walls to form line contacts with the side walls of the groove.

3. In a worm gearing, a worm comprising a cylincler having a curved concavity therein and having a cam groove in said concavity with the outer side wall thereof undercut toward the outer edge of said groove relative to planes perpendicular to the axis of the Worm, a cooperating worm gear of a radius substantially equal to that of the concavity having a tooth on the periphery thereof riding in said groove having curved side walls to form line contacts with the side walls of the groove.

4. In a worm gearing, a worm comprising a cylinder having a curved concavity therein and having a cam groove in said concavity with the outer side wall thereof undercut toward the outer edge of said groove relative to planes perpendicular to the axis of the worm, a cooperating worm gear of a radius substantially equal to that of the concavity having a plurality of teeth on the periphery thereof riding in said groove having curved side walls to form line contacts with the side walls of the groove.

ROBERT STEVENSON. 

